blk-throttle: add throtl_grp->service_queue

Currently, there's single service_queue per queue -
throtl_data->service_queue.  All active throtl_grp's are queued on the
queue and dispatched according to their limits.  To support hierarchy,
this will be expanded such that active throtl_grp's form a tree
anchored at throtl_data->service_queue and chained through each
intermediate throtl_grp's service_queue.

This patch adds throtl_grp->service_queue to prepare for hierarchy
support.  The initialization function - throtl_service_queue_init() -
is added and replaces the macro initializer.  The newly added
tg->service_queue isn't used yet.  Following patches will do.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Vivek Goyal <vgoyal@redhat.com>

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index ebaaaa9f57d6ed3b3015fa51d47af7ffe9766694..7340440ccfb5857428f5fa7ea83420738f33d378 100644 (file)
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -33,9 +33,6 @@ struct throtl_service_queue {
        unsigned long           first_pending_disptime; /* disptime of the first tg */
 };
 
-#define THROTL_SERVICE_QUEUE_INITIALIZER                               \
-       (struct throtl_service_queue){ .pending_tree = RB_ROOT }
-
 enum tg_state_flags {
        THROTL_TG_PENDING       = 1 << 0,       /* on parent's pending tree */
 };
@@ -60,6 +57,9 @@ struct throtl_grp {
        /* throtl_data this group belongs to */
        struct throtl_data *td;
 
+       /* this group's service queue */
+       struct throtl_service_queue service_queue;
+
        /*
         * Dispatch time in jiffies. This is the estimated time when group
         * will unthrottle and is ready to dispatch more bio. It is used as
@@ -190,11 +190,18 @@ alloc_stats:
                goto alloc_stats;
 }
 
+/* init a service_queue, assumes the caller zeroed it */
+static void throtl_service_queue_init(struct throtl_service_queue *sq)
+{
+       sq->pending_tree = RB_ROOT;
+}
+
 static void throtl_pd_init(struct blkcg_gq *blkg)
 {
        struct throtl_grp *tg = blkg_to_tg(blkg);
        unsigned long flags;
 
+       throtl_service_queue_init(&tg->service_queue);
        RB_CLEAR_NODE(&tg->rb_node);
        tg->td = blkg->q->td;
        bio_list_init(&tg->bio_lists[0]);
@@ -1168,8 +1175,8 @@ int blk_throtl_init(struct request_queue *q)
        if (!td)
                return -ENOMEM;
 
-       td->service_queue = THROTL_SERVICE_QUEUE_INITIALIZER;
        INIT_DELAYED_WORK(&td->dispatch_work, blk_throtl_dispatch_work_fn);
+       throtl_service_queue_init(&td->service_queue);
 
        q->td = td;
        td->queue = q;